Illumination apparatus, sensor unit, and reading apparatus

Abstract

An illumination apparatus includes a light source and an elongated light guide, wherein the light guide includes an emission surface that emits light from the light source and a reflection surface that reflects the light to the emission surface, the reflection surface includes a plurality of diffusion portions that diffuse the light, the diffusion portions have a shape of part of a sphere recessed from the reflection surface, a depth of the diffusion portions from the reflection surface is equal to or greater than 16.5% and equal to or smaller than 50% of a diameter of the sphere, and a width of the diffusion portions is equal to or greater than 0.1 mm and equal to or smaller than 50% of a width of the reflection surface.

What is claimed is: 
     
       1. An illumination apparatus comprising:
 a light source; and 
 an elongated light guide, wherein: 
 the light guide comprises an emission surface that emits light from the light source and a reflection surface that reflects the light to the emission surface, 
 the reflection surface comprises a plurality of diffusion portions that diffuse the light, 
 the diffusion portions have a shape of part of a sphere recessed from the reflection surface, 
 a depth of each of the plurality of the diffusion portions from the reflection surface is equal to or greater than 16.5% of a diameter of the sphere and equal to or smaller than 50% of the diameter of the sphere, and 
 a width of each of the plurality of the diffusion portions in a direction parallel to the reflection surface and orthogonal to a longitudinal direction of the light guide is equal to or greater than 0.1 mm and equal to or smaller than 50% of a width of the reflection surface. 
 
     
     
       2. The illumination apparatus according to  claim 1 , wherein
 the depth of each of the plurality of the diffusion portions from the reflection surface is equal to or greater than 35% of the diameter of the sphere and equal to or smaller than 50% of the diameter of the sphere. 
 
     
     
       3. The illumination apparatus according to  claim 1 , wherein
 the width of the diffusion portions is equal to or greater than 15% of the width of the reflection surface and equal to or smaller than 30% of the width of the reflection surface. 
 
     
     
       4. The illumination apparatus according to  claim 1 , wherein
 two to five diffusion portions are linearly arranged in the width direction of the reflection surface. 
 
     
     
       5. The illumination apparatus according to  claim 1 , wherein
 the light guide comprises inclined portions at boundaries of the reflection surface and the diffusion portions. 
 
     
     
       6. The illumination apparatus according to  claim 1 , wherein center points of any two diffusion portions immediately adjacent in the longitudinal direction of the light guide do not overlap such that the any two immediately adjacent diffusion portions are displaced in a width direction of the reflection surface. 
     
     
       7. A sensor unit comprising:
 an illumination apparatus; 
 a light condenser that focuses light reflected after the light is applied to an illuminated object by the illumination apparatus; and 
 a sensor that converts the light focused by the light condenser to an electrical signal, wherein: 
 the illumination apparatus comprises a light source and an elongated light guide, 
 the light guide comprises an emission surface that emits light from the light source and a reflection surface that reflects the light to the emission surface, 
 the reflection surface comprises a plurality of diffusion portions that diffuse the light, 
 the diffusion portions have a shape of part of a sphere recessed from the reflection surface, 
 a depth of each of the plurality of the diffusion portions from the reflection surface is equal to or greater than 16.5% of a diameter of the sphere and equal to or smaller than 50% of the diameter of the sphere, and 
 a width of each of the plurality of the diffusion portions in a direction parallel to the reflection surface and orthogonal to a longitudinal direction of the light guide is equal to or greater than 0.1 mm and equal to or smaller than 50% of a width of the reflection surface. 
 
     
     
       8. A reading apparatus comprising:
 a sensor unit comprising: an illumination apparatus; a light condenser that focuses light reflected after the light is applied to an illuminated object by the illumination apparatus; and a sensor that converts the light focused by the light condenser to an electrical signal; and 
 a movement portion that relatively moves at least one of the sensor unit and the illuminated object, wherein: 
 the illumination apparatus comprises a light source and an elongated light guide, 
 the light guide comprises an emission surface that emits light from the light source and a reflection surface that reflects the light to the emission surface, 
 the reflection surface comprises a plurality of diffusion portions that diffuse the light, 
 the diffusion portions have a shape of part of a sphere recessed from the reflection surface, 
 a depth of each of the plurality of the diffusion portions from the reflection surface is equal to or greater than 16.5% of a diameter of the sphere and equal to or smaller than 50% of the diameter of the sphere, and 
 a width of each of the plurality of the diffusion portions in a direction parallel to the reflection surface and orthogonal to a longitudinal direction of the light guide is equal to or greater than 0.1 mm and equal to or smaller than 50% of a width of the reflection surface.